4-CYCLE OVERHEAD VALVE ENGINES - Small Engine Discount

SERVICE
To remove the ignition module or the flywheel from
the engine, see Chapter 9 under "Disassembly".
GAP GAUGE
(670256)
SPARK PLUG SERVICE
Spark plugs should be removed, cleaned, and
adjusted periodically.
Check the air gap with a spark plug gap gauge and
adjust accordingly. Set the spark plug gap at .030"
(.762 mm) (diag. 5).
Replace the plug if the points on the base of the plug
are pitted or burned, or if the porcelain is cracked
anywhere.
When reinstalling the plug make sure it is clean of all foreign material.
NOTE: DO NOT USE A SAND BLASTER TO CLEAN PLUGS, MICROSCOPIC PARTICLES LEFT IN THE
PLUG CAN SCORE THE ENGINE CYLINDER DURING OPERATION. USE A SOLVENT AND A WIRE BRUSH
TO CLEAN, AND USING EYE PROTECTION, BLOW OUT THOROUGHLY WITH COMPRESSED AIR.
When replacing a spark plug consult the parts breakdown for the correct spark plug to be used in the engine
being serviced.
Install the spark plug in the engine and tighten it to 180 inch pounds (20.5 Nm) torque. If a torque wrench is not
available, screw the spark plug in as far as possible by hand, and use a spark plug wrench to turn the spark
plug 1/8 to 1/4 of a turn further if using the old spark plug, or 1/2 of a turn further if using a new spark plug.
5
CONDITIONS CAUSING FREQUENT SPARK PLUG FOULING
1. Carburetor setting is too rich or the air cleaner
is restricted.
2. Partially closed choke shutter.
3. Poor grade of gasoline.
4. Improper fuel.
5. Restricted exhaust system.
Normal
Carbon Deposit
6. Incorrect spark plug.
7. Incorrect spark plug gap.
8. Oil level is too high, or the breather is restricted.
9. Faulty piston rings.
10. Weak ignition system.
Worn
Oil Deposit
6
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